Metallic dibasic fatty soap based greases

ABSTRACT

MONOHYDROXY FATTY ACIDS OR ESTERS ARE CYANOETHYLATED AND THE CYANOETHOXY FATTY DERIVATIVES IS TREATED WITH DILUTE HYDROGEN PEROXIDE IN A WEALKY BASIC MEDIUM TO CONVERT THE CYANO GROUP TO AN AMIDE FUNCTION WHICH IS THEN HYDROLYZED TO THE DIBASIC ACID. THE DIBASIC ACID IS REACTED WITH AN APPROPRIATE METALLIC BASE SUCH AS LITHIUM, SODIUM AND CALCIUM TO MAKE THE DIBASIC SOAP WHICH IS DISPERSED A PETROLEUM OIL BASE OR A SYNTHETIC BASE OIL OF THE DIESTER TYPE OF FORM A GREASE.

United States Patent US. Cl. 260-413 4 Claims ABSTRACT OF THE DISCLOSURE Monohydroxy fatty acids or esters are cyanoethylated and the cyanoethoxy fatty derivative is treated with dilute hydrogen peroxide in a weakly basic medium to convert the cyano group to an amide function which is then hydrolyzed to the dibasic acid. The dibasic acid is reacted with an appropriate metallic base such as lithium, sodium and calcium to make the dibasic soap which is dispersed in a petroleum oil base or a synthetic base oil of the diester type to form a grease.

A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States Government, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to metallic dibasic fatty soaps and more specifically to the use of such soaps to make multi-purpose greases.

The addition of chemical compounds to lubricants is not new. In fact, certain chemical compounds are commonly added in small amounts to lubricants to improve their physical properties. Typical additives include oxidation or corrosion inhibitors, wear improvers, water repellants and dyes. One problem in a formulated grease containing additives is that in storage and in use these additives tend to migrate in the base oil and in extreme cases cause the grease to separate. Another problem is the frequent tendency for two additives to be incompatible. This often complicates the task of formulation.

The soaps of this invention improve the thermal stability and wear properties of the base oils with which they are mixed and thus decrease the need for additives to improve these properties. Another important aspect of this invention is that since the thermal stability, wear and grease forming properties are embodied in one molecule, it is impossible for migration or incompatibility to occur in the resulting grease.

In addition to being grease formers, the fatty derivatives of this invention impart thermal stability and anti-wear properties to the resulting greases. These derivatives also form greases with less than half the amount of soap normally used and they have the added feature of forming two classes of greases from two types of base oils; that is, diester type oils such as di-(2-ethylhexyl) sebacate (D.O.S.) and petroleum .oils such as 100 paraflin oil.

One object of this invention is to prepare stable greases by dispersing difunctional soaps in petroleum oil of lubricating viscosity.

Another object is to prepare stable greases by dispersing difunctional soaps in synthetic base oils of the diester type.

Still another object is to provide difunctional fatty soap derivatives that impart thermal stability and antiwear properties to greases.

In general, according to this invention the above objects are accomplished by dispersing in petroleum oil or in a synthetic base oil of the diester type, a dibasic fatty soap of the general formula:

wherein the sum of x and y is a number from 10 to 19 and R is a metallic ion capable of forming a fatty soap such as Na+, Li+ and 021*. As seen in the formula above, these fatty derivatives are novel compounds in which a 3 carbon side chain having a terminal carboxyl group is attached by an ether linkage to the carbon chain of the fatty soap.

Suitable starting materials for the greases formed in this invention are monohydroxy fatty acid or their ester derivatives either naturally occurring or synthesized by suitable known procedures. The monohydroxy fatty compounds are cyanoethylated by the method of oopending application, Ser. No. 852,469, filed Aug. 22, 1969, now US. Pat. No. 3,701,802, by dissolving them in acrylonitrile and adding a strong base to catalyze the reaction. The cyanoethoxy fatty derivative is then treated with dilute hydrogen peroxide in weakly basic medium. This treatment converts the cyano group to an amide function which is then hydrolyzed to the dibasic acid by refluxing with aqueous HCl. The resulting dibasic acid is then caused to react with the desired base and the dibasic soap is isolated. The grease can be made by adding the appropriate amount of dibasic soap (720%) to the base oil. If a synthetic diester oil such as di-(Z-ethylhexyl) sebacate (D.O.S) is used, the oil is heated to between 200220 C. and the soap added slowly with stirring. On cooling a stable grease forms. If a petroleum base oil is used, it is heated to 170-l75 C. and the dibasic soap added, and the mixture cooled slowly with stirring to form a grease.

The greases formed from dibasic fatty soaps and diester oils have good thermal stability and in the case of the disodium soap, exceptional good thermal properties. The anti-wear properties are also considerably better than a grease formulated from sodium stearate and a diester oil. The greases formed from the dibasic fatty soaps and petroleum oils also have better thermal stability and antiwear properties than the grease formed from sodium stearate and a petroleum oil.

In the preparation of the cyanoethoxy fatty grease precursor, suitable monohydroxy fatty acids may vary in chain length from 10-20 carbon atoms, and the hydroxy group may be attached at any point on the chain.

The cationic portions of the soap may be chosen from any of the elements commonly used in manufacturing soaps. For the purposes of this invention we have used lithium, sodium and calcium.

The greases formed from diester fluids can be formulated using any of the diester oils such as di-(2-ethylhexyl) sebacate ('D.'O.S.). Suitable oils for the petroleum based greases may be any hydrocarbon oil of lubricating viscosity such as paraffin oil.

The amount of dibasic soap used in this invention to form greases is less than 20% by weight of formulated grease. The greater the amount of soap used the harder the grease. In this invention, stable greases were made using 7-20% soap. The thermal and wear properties as measured by dropping point and four ball wear tester are improved at the higher percentages of soap.

In the preparation of the metal salts of these dibasic acids, it has been necessary to interpose the amide in the hydrolysis of the cyano function to the acid. Direct hydrolysis has been found practical JAOCS, 46, 1-4 (1969)]. The basic dibasic acids themselves, of course, are new and not found in the prior art.

The thermal stability properties of the greases described in this patent were determined using the dropping point method (A.S.T."M. D-566). This procedure measures the temperature at which the grease passes from a semisolid to a liquid state and is a qualitative indication of the heat resistance of the grease.

Anti-wear properties were determined using the Shell Four Ball Wear Tester as described by A.S.T.M. designation D226664T. Federal test method standard No. 7916. Approximately 10 ml. of the grease to be tested is placed in the test cup so that the three bottom stationary halls are covered. After positioning the cup on its stand in contact with the fourth ball the grease was heated to 75 C., a 40 kg. load was placed on the weight tray, and the upper ball was allowed to rotate at 1200 rpm. for 1 hour. The diameters of the scars worn on the three stationary balls were measured by means of a low power microscope. The results are shown in Table I. The hardness of the greases was determined with a Penetrometer as described by A.'S.T.M. designation D21748. A micro-cone was used to check the consistency of small samples. Some of the physical properties of the greases are shown in Table I.

The invention is exemplified as follows? Fifty grams (0.16 moles) of methyl 12-hydroxystearate was dissolved in 500 ml. (7.5 moles) of acrylonitrile containing 2.5 ml. water. To this mixture was added, rapidly with stirring, 10 ml. of a 40% aqueous solution of benzyltrimethylammonium hydroxide. Polymerization of the excess acrylom'trile occurred at four minutes. Fifty ml. of water containing 3 ml. B01 was added at this point. The resulting mixture was extracted with three 300 ml. portions of ether. The combined extracts were washed with water, dried over sodium sulfate and evaporated to a residue weight of 55.9 g. gas-liquid chromatography (G.L.C.) analysis confirmed that the residue was predominately methyl 12(2-cyanoethoxy) stearate. Recrystallization from hexane gave a 97-+% pure product. To a stirred solution of 50 g. (0.14 moles) of methyl 12(2-cyanoethoxy) stearate in 150 ml. ethanol at C. was added slowly at precooled C.) mixture of 500 ml. 7% aqueous hydrogen peroxide and 250 ml. 95% ethanol. The reaction mixture was adjusted to pH 10 by addition of dilute aqueous sodium hydroxide solution and stirred at 60 C. for 3 hours and then cooled to room temperature. The mixture was acidified with dilute HCl and extracted with three 500 ml. portions of ether. The combined extracts were washed with water, dried over anhydrous sodium sulfate and evaporated to a residual weight of 51 g. The infrared (I.R.) spectrum of the residue showed the cyano function was converted to amide. A solution of 51 g. (0.14 moles) of this amide derivative in one liter of 30% aqueous HCl was allowed to reflux for 2 hours, then cooled to room temperature and extracted with three 300 ml. portions of ether. The combined extracts were washed with water, dried over sodium sulfate, and evaporated to a solid white residue (52 g.). Thin layer chromatagraphy (T.LC.) and LR.

analysis indicated an essentially pure compound having.

strong bonds at 1705 cm.- (acid C=O'), 1100 cm.- (CO-C). A recrystallized sample had a melting point of 63-64 C. Elemental analysis showed the compound to be 12(2-carboxyethoxy)-stearic acid. From this diacid the following soaps were prepared:

62 g. (031-7 moles) of the above diacid was dissolved in 250 m1. acetone and 14.1 g. (0.35 moles) lithium hydroxide in ml. water was added to it with stirring. After stirring for 1 hour, 500 ml. acetone was added and the mixture filtered and the soap dried under vacuum at C. to give 5 8 g. of a white powder; melting point 1 65-175"; lithium content 4.08%.

Using the procedure described above, the disodium soap; m.p. 212125, sodium content 12.9%, and the dicalcium soap; m.p. 186-188, calcium content 9.58% were prepared.

PREPARATION OF DIESTER TYPE GREASE 1.5 g. of the disodium soap was added slowly with stirring to 8.5 g. di-(Z-ethylhexyl) sebacate at 220 C. After heating and stirring for 0.5 hours the mixture was allowed to slowly cool with stirring. The resulting product was a stable yellow grease.

Using the procedure described above the dilithium and dicalcium soap diester greases were prepared.

PREPARATION OF PETROLEUM TYPE GREASE 1.0 g. of the disodium soap was added slowly with stirring to 9.0 g. of 100 paraffin oil at C. After stirring at 170 C. for 0.5 hours, the mixture was allowed to cool. The resulting product was a dark brown grease.

Using the procedure described above the dilithium and dicalcium soap 100 paraffin oil greases were prepared.

TABLE I NGLI Wear Percent grade Dropping soar dia., Soap Base oil soap hardness point, F. mm.

Disodium D.O.S 20 4 500+ 0.643 10.0.3 15 3 500+ 0.686 D.O.S 10 1 332 0.760

Diealelum. D.O.S. 20 5 311 0. 755 D0. 15 3 274 0.790 D.O.S----..----.. 10 0 0.820

Dlsodium- 100 paraffin oil. 15 2 407 0. 523 -.do 10 1 340 0. 565

Dillthium --do 10 0 353 0. 596

Dicalcium -.d0- l5 2 0. 541 o 10 1 0.580

We claim:

1. A dibasic fatty soap of the formula ("n-0R (in.

' fingertip-{34011 -ii-o R wherein the sum of x and y is 15 and R is a metallic ion capable of forming a fatty soap.

2. The dibasic fatty soap of Claim 1 wherein R is lithium.

3. The dibasic fatty soap of Claim 1 wherein R is sodium.

4. The dibasio fatty soap of Claim 1 wherein R is calcium.

References Cited Chem. Abstracts, 74: 371 1w.

LEWIS GOTTS, Primary Examiner E. G. LOVE, Assistant Examiner US. Cl. X.R. 25239; 260404- 

